EHLO command: Identify the domain name of the sending host to SMTP

Rule: Send the EHLO command once before a MAIL FROM command.

Requirement: When the STARTTLS command is used, the EHLO command must also be used. Currently, the only mail extension that is supported by the CSSMTP application is the STARTTLS command. See STARTTLS command: Indicate the ability to negotiate the use of TLS for more information.